Gimp startup problems

I've looked on the web to no avail. I was hoping for some insight into a problem with gimp and X11. I recently upgraded from 10.4 to 10.5 and have broke my gimp installation. I get the following message when I try to start gimp:

I tried that, but when I opened the installer package, it said, "This system does not need this update." I couldn't click continue or next or anything, except cancel. Although, I did do the Software Update version before. Please help. In the mean time, I'm downloading the Tiger version of Gimp to see if that gets me anywhere.